Device for a water boiler provided with an overpressure furnace



J1me 1965 J. F. M. VAN DER MEULEN 3,187,72

DEVICE FOR A WATER BOILER PROVIDED WITH AN OVERPRESSUHE FURNACE Filed July 9, 1963 2 Sheets-Sheet 1 June 8, 1965 J. F. M. VAN DER MEULEN 3,137,726

DEVICE FOR A WATER BOILER PROVIDED WITH AN OVERPRESSURE FURNACE 2 Sheets-Sheet 2 Filed July 9, 1963 United States Patent 3,187,726 DEVICE FGR A WATER BUTLER PROVIDED WITH AN OVERPRESSURE FURNAQE Josephus Franciscus Maria van der Meulen, Marconistraat 6, Eindhoven, Netherlands Filed July 9, 1963, Ser. No. 293,641 Claims priority, applicatior lggtherlands, July 10, 1962,

28 7 Claims. (Cl. 122-449) V The invention relates to a water boiler provided with an overpressure furnace, with an oil burner, and with a blower for the supply of air. The boiler further includes flue tubes between a flame chest on the rear side of the boiler and a combustion gas chamber on the front side of the boiler. Such a boiler has heretofore been suggested but without success because of substantial difficulties.

The difficulties consist in that there is a comparatively small range of adjustment and only a moderate efi'iciency of the boiler, while often inconveniences are experienced on starting the boiler. The enlargement of the possibility of regulation may be obtained by an increase or decrease of the flow resistance of the combustion gases along their path between the flue chest and the combustion gas chamber. This modification of the flow resistance makes special demands on the supply of combustion air to the burner and consequently on the blower and on the way from the blower to the furnace which is to be covered by the air. It is an object of the present invention to provide a solution for these problems.

Experiments have revealed that for the purpose of being able to regulate perfectly the capacity of the boiler, while simultaneously maintaining the efilciency, the following demands are necessary to be made on the air supply. This supply of air must first of all be very regular, that is, the air fed to the burner is not allowed to exhibit local differences of velocity nor diiferences in the direction of fiow. The blower, too, must produce a current of air which is as regular as possible, without pulsations and with as little turbulence as possible. In addition the blower must be capable of producing a rapid increase of pressure at a minor increase of the flow resistance. It is further of importance that the air supplied to the burner be pro-heated, whereby the thermal efiiciency of the boiler installation can be improved, such that less difiiculty will be experienced during use of heavy fuel.

It is an object of the invention to provide a boiler which meets these requirements. According to the invention this is attained in that the pressure side of the blower is connected to a blast box with intermediate partitions,

said box being provided within the combustion gas chamher, the said partitions imposing a zigzag path on the blower air before the same reaches the centrally arranged burner, the blower consisting of a radial compressor with a steep Q-H characteristic, i.e., relatively small change in flow quantity for relatively large pressure variation. Due to these features the combustion air on reaching the burner constitutes a very uniform and pre-heated flow by means of which it is possible to obtain a very stable and effective flame formation in the furnace.

A further object of the invention is to achieve a great stability in the operation of the centrifugal blower by connecting the suction side of the blower to a substantially straight duct the length of which is in the order of the distance traversed by the sucked air in about 1 second. Thereby a standing column of air is provided which facilitates starting of the boiler. Also the length of the duct insures a regular flow of air to the blower substantially free of turbulence. 7

It has been found that this duct is of great importance for starting the boiler, since often difiiculties are experienced in the flame formation in the furnace, these ICC difiiculties being avoided due to the application of the said suction duct. The provision of the blast box within the combustion gas chamber not only ensures a heating of the combustion air, but also a cooling of the combustion gases, escaping toward the chimney.

In order to obtain the above-mentioned effect of a constant supply speed of the air for the burner without pulsations or turbulence it is desirable that the expansion of the air and consequently the increase in velocity take place very gradually. It is therefore a further object of the invention that the air passage section beginning from the disc-shaped front portion of the blast box to the space around the centrally positioned burner be made constant or slightly decreasing.

The invention further aims at making it possible to use a heavy oil in the burner, without any difiiculties relative .to ignition.

It is still a further object of the invention to unite the blast box with the burner and to make it easy to inspect the interior of the boiler. Other and further objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which: i

FIG. 1 shows a side elevation of the complete boiler installation;

FIG. 2 is a horizontal longitudinal section to an enlarged scale of the front portion of the boiler according to FIG. 1;

FIG. 3 shows on a still further enlarged scale a Variant of a detail of the burner head;

FIG. 4 is another embodiment of the burner head according to FIG. 3.

The water boiler represented in FIG. 1 is built up from a body 1 enclosing a furnace 2, which on the rear side is connected to a flue chest 3, while on the front side there is provided a combustion gas chamber 4. A number of fire or flue tubes 5, connecting the line chest 3 with the combustion gas chamber 4 are arranged in an annular configuration around the furnace 2. The boiler is connected to a chimney by way of an eduction stub 25.

The front side of the furnace 2 of the boiler installation which to an enlarged scale is represented in FIG. 2, is provided with an oil burner 6. The boiler operates with air 7 the blast boxfi are two concentrical and tubular interthe front side of the boiler) and mediate partitions 11 and 12, the partition 11 being connected with the front wall 13 of the disc shaped front portion 9 of the blast box, the portion 12 being connected with a conical rear wall 14 of the blast box.. Arranged with spaced relationship in respect to wall 14 is a conical shield plate 15, which is joined'to the end of the tubular intermediate partition 12 protruding into the furnace 2.

The blast box 8 is integral with the burner 6 and the blower 7 and is hingedly connected on one side with.

the body .1 of the boiler. This hinge is visible in FIG. 2 and is constituted by two arms 16 and 17 which are pivotally connected at 18. As is also visible in FIG. 2 the sealing between the slewing blast box (constituting the fixed portion of the boiler is formed by two rings 19 and 20 of refractory sealing material, the said rings being positioned against the rear side of the disc shaped frontpart and the outer wall of the cylindrical portion 16, respectively.

Further details of the oilburner 6 are not indicated as they are conventional. For Completeness sake, attention is drawn to the stabilizer disc 21,.which defines an annular passage between its rim and the tubular wall 12. The annular passage is relatively narrow being only in the order of a few millimeters. A hole is formed in the disc 21 .to allow for the passage of an atomized fuel jet, while in the remaining portion of the disc, helical slits are provided in order to generate a turbulence of the air Within the furnace 2. For strength considerations, several connecting strips 22 are provided within the blast box 8.

Connected to the suction side of the centrifugal blower.

7 is a substantially straight duct 23, the length of which is in the order of the distance which is traversed by the sucked air in about 1 second. The duct 23 has a substantially constant cross-section as. seen in FIG, 1. The free end 24 of the duct opens into the atmosphere.- Due to this column of air in the duct 23 the effect of the blower 7 is improved to such an extent that the difficulties often experienced in starting the boiler installation are entirely eliminated. The centrifugal blower 7 is of the kind having a steep Q-H characteristic (wherein Q represents the while moreover a decrease in sound is obtained. The

' stabilizer disc 21 is reduced to a diameter lying within quantity delivered, and H represents the delivery pressure) whereby upon a slight increase of resistance in the. passage of the combustion gases, there is immediately produced an in'crease'of pressure without a noticeable decrease of the output of the blower.

In operation, the pressure air from the blower 7 enters into the discshaped portion 9 of the blast box 8 and collides with the rear wall of this portion 9 so that the direction of flow is changed. Hereupon the air flows in a zigzag path through the central cylindrical part 10 around the free protruding ends of the intermediate walls 11 and 12 so as to arrive in the central region of the blast box around the burner 6-and to flow therefrom along and through the stabilizer disc 21 into the furnace 2. It has been found that due to this rather long path covered by the air before arriving in the furnace 2 there is obtained a very uniform flow at the location of the burner 6. Thus, each irregularity due to the direction of flow which the air may have on discharging from the centrifuga-l blower 7 is eliminated.

Due to the provision of the blast box within the combustion gas chamber 4 there is not only obtained a com pact, and as a result of the articulated arrangement, an

easily inspected structure, but moreover the thermal effi-.

ciency is enhanced by the transfer of heat between the combustion gases escaping to the chimney by way of the 'eduction stub 25 and the combustion air streaming into the blast box.

It should bev noted that the zigzag track within the blast box 8 according to a modified embodiment can be enlarged by lengthening the tubular intermediate walls 11 and 12 outwardly, the end of the tube 11 which protrudes from the front side of the boiler being closed by a cover, the supply duct for the fuelleading to the oil burner 6 traversing said cover. 7

The passage section for theair from the blower 7 in the zigzag path should remain constant or should decrease somewhat, in order to obtain a gradual transformation of pressure into velocity. In this respect it should .be noted that during this transformation the specific vol ume increasesless rapidly than the air velocity. V

In the variant according to FIG. 3 a tubular jacket 25 'is mounted concentrically around the ,burner 6 within the inner partition wall 12. This jacket has a number of passage holes26 near the front wall 13, said holes serving to feed a quantity of air out of the zig-zag path into the jacket. The size of these holes is such that during operation a pressure inside the jacket is developed, said pressure being smaller than the pressure between the jacket andthe wall 12 Preferably, the decrease of pressure does not exceed 50% of the pressure between the jacket and wall 12. This additional jacket is of importance in connection with the use of a heavy oil as fuel,

the jacket 25.

The embodiment according to FIG..4 differs from the variant according to FIG. 3 by the truncated conical end :27 of the jacket 25 joining the central opening 28 in the stabilizer disc 21.

Although the present invention has been disclosed in connection with a few preferred embodiments thereof, variations and modifications may be effected by those skilled in the art without departing from the principles of the invention, as disclosed in the foregoing description and defined by the appended claims.

What is claimed is: V

1.- A water boiler comprising an overpressure furnace including an oil burner, and a centrifugal blower for the supply of air for said burner, said boiler further including a flue chest and a combustion gas chamber located at opposite ends of the boiler, flue tubes between said flue chest and the combustion gas chamber for the flow of combustion gases from the former to the latter, a substantially straight duct connected to said blower for the supply of air thereto, the duct having a length which is in the order of the distance traversed by the sucked air in about one second, said duct having a substantially constant cross-section and extending proximate the flue chest, combustion gas chamber, and flue tubes, a blast box within the furnace, the pressure side of the blower opening at right angles into said blast box, said blast box including opposite, front and rear walls and at least two interme diate partitions,,said box being adjacent and partially enclosing the combustion gas chamber, said front and rear walls defining a disc-shaped front portion upon which the blower is mounted and a cylindrical portion which is centrally connected to the front portion, said cylindrical portion having a depth substantially corresponding with the depth of the combustion gas chamber, said intermediate partitions being concentrically disposed within said cylindrical portion, said, oil burner hing centrally arranged in said blast box, said partitionsbeing alternately connected with the front and rear Walls of the blast box and being spaced from one another to define a zig-zag path for the air supplied by the blower before the air reaches the centrally arranged burner, said blower being a radial compressor.

2.;A water boiler comprising an overpressure furnace having an inlet end and an opposite outlet end, a flue chest and a combustion gas chamber, said flue chest and gas chamber being located at opposite ends of the furnace, flue tubes between said flue chest and said combustion gas chamber for the flow of combustion gases from the furnace via the flue chestand the flue tubes to the bustion gas chamber, a blast box concentric with said burner for the supply of air to said burner, said blast box including a circumferential wall surrounded by the combustion gas chamber, said blast box further including an outwardly directedwall on the front end of said circumferential wall, said outwardly directed wall defining a closure for the front end of the combustion gas chamber, said blast box further including a front wall parallel to and spaced from said outwardly directed wall, a radial air compressor mounted on said front wall and having an opening for discharge of air at right angles to said front wall into the portion of the-blast box between said front wall and said outwardly directed wall, said blast box further having a rear wall extending inwardly from the rear end of said circumferential wall toward and terminating spaced from said burner, at least two intermediate partitions concentrically disposed within said blast box WL awhereby the air reaches the burner in a uniform nonturbulent axially directed flow.

3. A Water boiler according to claim 2, comprising a substantially straight inlet duct connected to the blower for the supply of air thereto, said duct having a length which is in the order of the distance traversed by the sucked air in about one second, said duct having a substantially constant cross-section.

4. A water boiler according to claim 2 wherein the air passage sect-ion beginning from the portion of the blast box between the front wall and the outwardly di rected wall to the space around the centrally positioned burner is substantially constant.

5. A Water boiler according to claim 2 comprising a tubular jacket accommodated within the inner intermediate partition and concentrically around the burner, sa-id jacket having a number of passage holes defining a collective inlet area for the supplied air such that during operation, a decrease in pressure inside the jacket occurs which is less than 50% of the pressure outside the jacket.

6. A water boiler according to claim 2 comprising means hingedly securing the blast box to the body of the furnace such that the blast box constitutes one end of the furnace.

7. A water boiler according to claim 2 wherein the partition connected to the front wall is an outer cylindrical partition and the partition connected to the rear wall is an inner cylindrical partition extending within the outer cylindrical partition in spaced relation and surrounding the oil burner, said partitions having ends remote from the walls with which they are respectively connected which are spaced from the other of the walls.

References Cited by the Examiner UNITED STATES PATENTS 1,986,914 1/35 Avery 122-149 2,287,057 6/42 Page 122-149 2,674,981 4/54 Clarkson 122-149 X 2,835,230 5/58 Cleaver et al. 122-149 2,986,206 5/61 Boelsma 158-1.5 X 3,033,271 5/62 Schwander 158-1.5 3,049,173 8/62 Costello et a1 158-1.5 XR 3,070,151 12/62 Goossens 158-76 FOREIGN PATENTS 254,618 7/26 Great Britain. 267,857 3/27 Great Britain.

OTHER REFERENCES relied on).

PERCY L. PATRICK, Primary Examiner. KENNETH W. SPRAGUE, Examiner. 

1. A WATER BOILER COMPRISING AN OVERPRESSURE FURNACE INCLUDING AN OIL BURNER, AND A CENTRIFUGAL BLOWER FOR THE SUPPLY OF AIR FOR SAID BURNER, SAID BOILER FURTHER INCLUDING A FLUE CHEST AND A COMBUSTION GAS CHAMBER LOCATED AT OPPOSITE ENDS OF THE BOILER, FLUE TUBES BETWEEN SAID FLUE CHEST AND THE COMBUSTION GAS CHAMBER FOR THE FLOW OF COMBUSTION GASES FROM THE FORMER TO THE LATTER, A SUBSTANTIALLY STRAIGHT DUCT CONNECTED TO SAID BLOWER FOR THE SUPPLY OF AIR THERETO, THE DUCT HAVING A LENGTH WHICH IS IN THE ORDER OF THE DISTANCE TRAVERSED BY THE SUCKED AIR IN ABOUT ONE SECOND, SAID DUCT HAVING A SUBSTANTIALLY CONSTANT CROSS-SECTION AND EXTENDING PROXIMATE THE FLUE CHEST, COMBUSTION GAS CHAMBER, AND FLUE TUBES, A BLAST BOX WITHIN THE FURNACE, THE PRESSURE SIDE OF THE BLOWER OPENING AT RIGHT ANGLES INTO SAID BLAST BOX, SAID BLAST BOX INCLUDING OPPOSITE, FRONT AND REAR WALLS AND AT LEAST TWO INTERMEDIATE PARTITIONS, SAID BOX BEING ADJACENT AND PARTIALLY ENCLOSING THE COMBUSTION GAS CHAMBER, SAID FRONT AND REAR WALLS DEFINING A DISC-SHAPED FRONT PORTION UPON WHICH THE BLOWER IS MOUNTED AND A CYLINDRICAL PORTION WHICH IS CENTRALLY CONNECTED TO THE FRONT PORTION, SAID CYLINDRICAL PORTION HAVING A DEPTH SUBSTANTIALLY CORRESPONDING WITH THE DEPTH OF THE COMBUSTION GAS CHAMBER, SAID INTERMEDIATE PARTITIONS BEING CONCENTRICALLY DISPOSED WITHIN SAID CYLINDRICAL PORTION, SAID OIL BURNER BING CENTRALLY ARRANGED IN SAID BLAST BOX, SAID PARTITIONS BEING ALTERNATELY CONNECTED WITH THE FRONT AND REAR WALLS OF THE BLAST BOX AND BEING SPACED FROM ONE ANOTHER TO DEFINE A ZIG-ZAG PATH FOR THE AIR SUPPLIED BY THE BLOWER BEFORE THE AIR REACHES THE CENTRALLY ARRANGED BURNER, SAID BLOWER BEING A RADIAL COMPRESSOR. 